Bring 6 quarts of salted water to a boil in an 8-quart pot over high heat. Stir the spaghettini into the boiling water. Return to a boil, stirring frequently. Cook the pasta, semi-covered, stirring occasionally, until tender but still very firm, about 6 minutes.

Meanwhile, heat 3 tablespoons of the olive oil in a large skillet over medium heat. Add the garlic and cook, shaking the skillet and stirring, until pale golden, about 2 minutes. Remove from the heat and add crushed red pepper.

Ladle about 1 1/2 cups of the pasta cooking water into the sauce. Add the remaining 2 tablespoons olive oil and salt to taste.

If the skillet is large enough to accommodate the sauce and pasta, fish the pasta out of the boiling water with a large wire skimmer and drop it directly into the sauce in the skillet. If not, drain the pasta, return it to the pot, and pour in the sauce. Bring the sauce and pasta to a simmer, tossing to coat with sauce. Cook until the pasta is coated with the sauce and done, about 1 minute. Remove the pot from the heat and toss in the grated cheese, if using. Check the seasoning, adding salt and crushed red pepper if necessary. Serve immediately in warm bowls.

I use one small can of chicken broth, which I heat in the skillet before adding the pasta and pasta water.